#include "Helper.hpp"

namespace Helper {

    //
    //  https://stackoverflow.com/questions/5288076/base64-encoding-and-decoding-with-openssl
    //  Thanks Omnifarious
    //  OpenSSL's base64 API is too dreadful to use
    //
    static const char b64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    static const char b64_reverse_table[128] = {
            64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
            64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
            64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
            64,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64, 64,
            64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64
    };

    std::string base64_encode(const std::vector<uint8_t>& bindata) {
        using bytes = std::vector<uint8_t>;

        if (bindata.size() > (std::numeric_limits<bytes::size_type>::max() / 4u) * 3u) {
            throw ::std::length_error("Converting too large a string to base64.");
        }

        const std::size_t binlen = bindata.size();
        // Use = signs so the end is properly padded.
        std::string retval((((binlen + 2) / 3) * 4), '=');
        std::size_t outpos = 0;
        int bits_collected = 0;
        unsigned int accumulator = 0;
        const bytes::const_iterator binend = bindata.end();

        for (auto i = bindata.begin(); i != binend; ++i) {
            accumulator = (accumulator << 8) | (*i & 0xffu);
            bits_collected += 8;
            while (bits_collected >= 6) {
                bits_collected -= 6;
                retval[outpos++] = b64_table[(accumulator >> bits_collected) & 0x3fu];
            }
        }
        if (bits_collected > 0) { // Any trailing bits that are missing.
            assert(bits_collected < 6);
            accumulator <<= 6 - bits_collected;
            retval[outpos++] = b64_table[accumulator & 0x3fu];
        }
        assert(outpos >= (retval.size() - 2));
        assert(outpos <= retval.size());
        return retval;
    }

    std::vector<uint8_t> base64_decode(const std::string& ascdata) {
        std::vector<uint8_t> retval;
        const std::string::const_iterator last = ascdata.end();
        int bits_collected = 0;
        unsigned int accumulator = 0;

        for (std::string::const_iterator i = ascdata.begin(); i != last; ++i) {
            const int c = *i;
            if (::std::isspace(c) || c == '=') {
                // Skip whitespace and padding. Be liberal in what you accept.
                continue;
            }
            if ((c > 127) || (c < 0) || (b64_reverse_table[c] > 63)) {
                throw ::std::invalid_argument("This contains characters not legal in a base64 encoded string.");
            }
            accumulator = (accumulator << 6) | b64_reverse_table[c];
            bits_collected += 6;
            if (bits_collected >= 8) {
                bits_collected -= 8;
                retval.emplace_back(static_cast<uint8_t>((accumulator >> bits_collected) & 0xffu));
            }
        }
        return retval;
    }

}

